The present invention is directed to the catalytic reforming of hydrocarbons. More particularly, this invention is concerned with catalytic reforming in the presence of molecular hydrogen of naphthene and paraffin-containing hydrocarbon fractions boiling in the gasoline or naphtha range, in a multiple fixed bed catalyst conversion system employing both a supported platinum-group metal and rhenium.
In a plurality of reforming zones such as disclosed in U.S. Pat. Nos. 3,392,107 (1968), 3,705,094 (1972), and 3,705,095 (1972) which are expressly and totally incorporated herein by reference, a supported platinum-group metal catalyst having an unskewed distribution was found at unpredictable intervals to lose both activity and selectivity in the earlier zones at a faster rate than was expected. Even employing reactivation procedures such as disclosed in U.S. Pat. Nos. 3,637,524 (1972) and 3,781,219 (1973), both expressly incorporated herein by reference, did not significantly improve this situation. In fact, the reactivation procedure was less effective in restoring the overall activity and selectivity to the platinum-group metal catalyst in the earlier zones than was predicted based upon the more usual performance of such catalysts.
Regeneration throughout this specification and the claims means the process wherein at least a portion of carbonaceous deposits on a reforming catalyst are removed by an oxidative burn-off. Carbonaceous deposits can form on a reforming catalyst during reforming of a hydrocarbon feed.
Reactivation throughout this specification and the claims means the process wherein a previously regenerated catalyst is further treated to disperse or redistribute the supported platinum-group metal and/or to redistribute and recomposite the halogen content of the catalyst to maintain catalytic activity.